Cryo-ablation refrigerant distribution catheter

ABSTRACT

Described herein are methods and devices for performing ablation via a cryoablation catheter. An ablation catheter having a cyroablation chamber at its distal end can be used to achieve a uniform ablation band in or around the pulmonary veins. The cyrochamber can house a dispersion member in fluid communication with a refrigerant supply and can function to evenly distribute received refrigerant over some portion of the inner wall of the cryochamber. As a result of this even distribution of refrigerant within the cyrochamber, uniform ablation of the targeted tissue of the patient can be achieved.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/402,970, filed Mar. 12, 2009, now U.S. Pat. No. 8,579,890; whichclaims priority to Provisional Application Ser. No. 61/064,577 entitled“Cryo-Ablation Refrigerant Distribution Catheter” filed Mar. 13, 2008,the entire disclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Atrial fibrillation is the most common heart arrhythmia in the world,affecting over 2.5 million people in the United States alone. Infibrillation the upper chambers of the heart, known as the atria, quiverrapidly instead of beating in a steady rhythm. The rapid quiveringreduces the heart's ability to properly function as a pump.

The disorder typically increases the risk of acquiring a number ofpotentially deadly complications, including thrombo-embolic stroke,dilated cardiomyopathy, and congestive heart failure. Quality of life isalso impaired by atrial fibrillation symptoms such as palpitations,chest pain, dyspnea, fatigue, and dizziness. People with atrialfibrillation have, on average, a five-fold increase in morbidity and atwo-fold increase in mortality compared to people with normal sinusrhythm.

Treatments for atrial fibrillation include drug therapy,electrocardioversion, and surgical or intravascular ablation techniques.Surgical ablation is an invasive procedure whereby the surgeon creates amaze-like pattern of incisions on the inside of the patient's atria. Thescarring that results acts to block the abnormal electrical pathways inthe heart that lead to atrial fibrillation. Surgical ablation has a muchhigher success rate than drug therapies and lacks the potential for sideeffects presented by drug treatment. However, highly invasive (e.g.,open-chest) procedures can present substantial risks.

Intravascular ablation similarly creates scar tissue that impedes thetravel of errant electrical impulses in the heart tissue. Radiofrequency and microwaves are exemplary energy sources for such ablation.Additionally, cryoablation techniques have also been explored.

One benefit of radio frequency, microwave, and cryoablation is theability to deliver therapy via a catheter. These ablation techniques usea less invasive, transvenous approach. To perform such a procedure,specifically a cryoablation procedure, the tip of a cryoablationcatheter is typically inserted into and advanced within the vasculatureof a patient until the tip is located adjacent to the targeted tissue.Next, in a typical cryocatheter, a refrigerant is pumped into thecatheter for expansion into an expansion chamber that is located at ornear the catheter tip. The expansion of the refrigerant cools thecatheter tip and target tissue. By cooling the tip of a cryoablationcatheter to sub-zero temperatures, the cells in the heart responsiblefor conducting the arrhythmia are altered so that they no longer conductelectrical impulses. However, in some instances, the refrigerant is notevenly distributed within the desired region of the expansion chamber.This results in the non-uniform or uneven ablation of the targetedtissue.

Accordingly, current treatments for atrial fibrillation could benefitfrom improved techniques and devices for cyroablating the cells in theheart responsible for conducting cardiac arrhythmias.

SUMMARY OF THE INVENTION

Described herein is a cryoablation catheter for use in tissue ablation.The catheter comprises an elongate supply lumen, or catheter body, whichcarries a cryofluid or refrigerant from a refrigerant supply unit.Generally, a source of refrigerant is connected to the proximal end ofthe supply lumen and the cryochamber, or expansion chamber, is locatedat the lumen's distal end. The ablation catheter also comprises arefrigerant dispersion member. The dispersion member, located near thedistal end of the supply lumen, is at least partially housed by theexpansion chamber and serves to evenly distribute the refrigerantexiting the distal end of the supply lumen across at least some portionof the interior of the expansion chamber. An even distribution ofcryofluid can facilitate proper ablation procedures by reducing the riskof inconsistent cooling of the targeted tissue in contact with theablation catheter tip.

In one aspect, the catheter described herein can be used for performingablation near or within the pulmonary veins of the heart where a uniformcircumferential ablation band across the targeted tissue is desired.However, the devices described herein are not limited to cardiacapplications.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of theinvention and together with the description, serve to explain theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of one embodiment of a cryoablation systemdisclosed herein.

FIG. 2A is a cross-sectional side view of one embodiment of acryoablation catheter disclosed herein.

FIG. 2B is a cross-sectional front view of one embodiment of acryoablation catheter disclosed herein.

FIG. 2C is a cross-sectional front view of one embodiment of acryoablation catheter disclosed herein.

FIG. 3A is a side view of one embodiment of a cryoablation catheterdisclosed herein.

FIG. 3B is a cross-sectional side view of one embodiment of acryoablation catheter disclosed herein.

FIG. 4A is a cross-sectional side view of one embodiment of acryoablation catheter disclosed herein.

FIG. 4B is a cross-sectional side view of one embodiment of acryoablation catheter disclosed herein.

FIG. 5A is a cross-sectional side view of one embodiment of acryoablation catheter disclosed herein.

FIG. 5B is a front view of one embodiment of a cryoablation catheterdisclosed herein.

FIG. 6A is a side view of one embodiment of a cryoablation catheterdisclosed herein.

FIG. 6B is a cross-sectional side view of one embodiment of acryoablation catheter disclosed herein.

FIG. 7 is a cross-sectional side view of one embodiment of acryoablation catheter disclosed herein.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Disclosed herein are various embodiments of a cryoablation catheterdevice. Generally, the device allows an operator to cool tissue targetedfor ablation in a consistent and/or uniform fashion. As part of variousprocedures, where ablation is to be performed in or around the pulmonaryveins, it may be desirable to evenly cool the tissue in acircumferential band. Cryoablation catheters known in the art, in whichrefrigerant is simply released into the cryochamber, can result in anuneven distribution of cryofluid on a desired region of the interiorwall of the cryochamber or uneven cooling of the targeted tissue. This,in turn, can necessitate additional ablations and extend procedureduration. The cyroablation catheter disclosed below solves this problemby positioning a dispersion member or dispersion body within thecyrochamber. In one aspect, the dispersion member serves to direct thecryofluid towards the interior wall of the expansion chamber in such away as to ensure even distribution of the cryofluid over the desiredarea of the expansion chamber and/or even cooling of the targetedtissue. This can result in reliable and uniform ablation of thesurrounding tissue.

While the ablation devices described herein focus on epicardialablation, one skilled in the art will appreciate that the catheterdevices, systems, and methods of use described below can permit ablationof a variety of anatomic structures. In one aspect, a cyroablationcatheter is sized and shaped for ablating cardiac tissue. In anotheraspect, the catheter is configured specifically for ablation at theostium of the pulmonary veins or surrounding tissue. However, themethods and devices described herein can be used for other, non-cardiacprocedures.

Reference will now be made in detail to the exemplary embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

FIG. 1 illustrates one exemplary embodiment of a cyroablation system 100for ablating tissue with cryofluid comprising an ablation device 102 anda cyrofluid or refrigerant supply unit 104. In one aspect, device 102can include an elongate catheter body 106 extending between proximal anddistal ends 108 and 110, respectively. An expandable member 200, intowhich cyrofluid can be placed as will be discussed in more detail below,can be coupled with distal end 108 of elongate catheter body 106 suchthat the expandable member and the catheter body are in fluidcommunication.

In one aspect, catheter body 106 can be defined by a flexible or rigidbody having one or more channels through which treatment fluids can bedelivered. For example, catheter body 106 can include at least one lumenfor the delivery of a cryofluid and/or at least one lumen for theexhaust of spent refrigerant. In addition, wires for conductingtherapeutic energy and/or for sending/receiving sensed signals canextend along at least a portion of catheter body 106.

The catheter body can also include a variety of features to facilitateinsertion and/or placement of expandable member 200 relative to targettissue. In one embodiment, device 102 can include an articulatingsegment defined by a portion of catheter body 106. For example, a distalportion of body 106 can be actuated by a user from a proximal locationto steer expandable body into a target location. In one exemplaryaspect, catheter body 106 can include push and/or pull strands totransmit forces to the articulation segment.

The size and shape of catheter body 106 can be chosen based on theintended use of device 102. Where device 102 is used for cardiacablation, catheter body 106 can be sized and shaped for insertionthrough a vascular lumen. In addition, the materials and structure ofcatheter body 106 can be chosen to provide a flexible elongated body.One skilled in the art will appreciate that catheter body 106 canrepresent the variety of catheter structures commonly known in the artfor a vascular approach. However, the devices described herein need notbe delivered via a transvenous route and/or the target tissue need notbe cardiac tissue.

A user interface or handle 112 can be coupled to proximal end 108 ofcatheter body 106, permitting a clinician to grasp device 102. Handle112 can have a variety of forms depending on the intended use of device102 and/or the environment in which device 102 is used. In one aspect,handle 112 can include one or more sources of liquid or gas forexpanding expandable member 200. Controls for governing the delivery ofliquid, such as a cryofluid or volume displacement fluid, can, in oneaspect, also be located on handle 112. Alternatively, or additionally,handle 112 can be configured to mate with one or more sources of liquidsuch as refrigerant supply unit 104. In one embodiment, supply unit 104includes a cryofluid and/or volume displacement fluid. Additionally,supply unit 104 can maintain the cryofluid under high pressure. Amongthose fluids commonly used for cyroablation are liquid nitrous oxide,liquid carbon dioxide, and/or fluorocarbons, but any other gas, fluid,or refrigerant known in the art can also be used. In another aspect,supply unit 104 can further include a mechanism for regulating andcontrolling expansion of expandable member 200 via delivery of fluid.

Referring now to FIG. 2A, one exemplary embodiment of cyroablationcatheter 102 is shown. Specifically, distal end 110 of catheter body 106and expandable member 200 are depicted. In one aspect, catheter body 106can be comprised of a supply lumen 114, having a proximal end 116 (notpictured) and a distal end 118, and an exhaust lumen 120, having aproximal end 122 (not pictured) and a distal end 124. In one embodiment,the supply lumen and the exhaust lumen can be concentrically positioned,the supply lumen residing within the exhaust lumen. In otherembodiments, however, this may not be the case. For example, in anotherembodiment, the exhaust lumen may reside within the supply lumen or thetwo lumens could be positioned side by side. Further, in otherembodiments, there can be additional lumens serving other functions,such as providing a volume displacement fluid, separate from thecyrofluid, to expandable member 200.

In another aspect of the embodiment depicted, expandable member 200 canbe comprised of a cyrochamber 126 housed within an exhaust chamber 128.These expandable chambers or balloons can be comprised of any suitablematerial commonly used in the art. In one embodiment, cyrochamber 126and exhaust chamber 128 can be comprised of a polyurethane. In otherembodiments, however, they can be comprised of another material. In someembodiments, the chambers can be rigid structures comprised of anon-expandable material. Additionally, in different embodiments, therecan be an additional balloon or chamber that houses exhaust chamber 128.This additional balloon can serve to protect the patient should arupture in the cryochamber and/or exhaust chamber occur.

Again referring to FIG. 2A, in another aspect, cryochamber 126 can becoupled to, and in fluid communication with, distal end 118 of supplylumen 114. Similarly, exhaust chamber 128 can be coupled to, and influid communication with, distal end 124 of exhaust lumen 120. Thesecouplings can be airtight and achieved in various ways. For example, inone embodiment, cyrochamber 126 and/or exhaust chamber 128 can beadhesively coupled to the distal ends of the catheter lumens. In anotherembodiment, the chambers can be mechanically mated to the distal ends ofthe lumens. For example, the chambers can be threadedly or frictionallymated to the lumens. Alternatively, the chambers and the lumens could beintegrated such that they are a single piece. Other embodiments mayincorporate different methods of fastening the chambers to the distalends of the lumens.

A dispersion member 130 can reside within cyrochamber 126. In theembodiment depicted, dispersion member 130 resembles a plate-likemember, circular in a plane parallel to cross-section B-B and having arelatively flat surface facing distal end 118 of supply lumen 114. Asdiscussed below, however, in other embodiments, the shape of dispersionmember 130, particularly the shape of the surface facing the distal endof supply lumen 114, can depend on the desired flow of the refrigerantwithin cyrochamber 126. For example, in other embodiments, dispersionmember 130 can be conically or pyramidally shaped. In other embodiments,the surface of dispersion member 130 facing the distal end of supplylumen 114 can be convex or concave in shape. Alternative embodiments cancomprise dispersion members of other various shapes.

In one aspect, the dispersion member can be mated and/or coupled to oneof the catheter lumens so as to anchor the dispersion member within thecyrochamber. For example, the dispersion member can be mated to theinner surface of the supply lumen in such a way as to still allowpassage of the refrigerant.

In the embodiment depicted, dispersion member 130 can be anchored inplace within cyrochamber 126 through the use of stem 132 having aproximal end 134 and a distal end 136. In one aspect, distal end 136 ofstem 132 can be coupled to dispersion member 130 while the proximal end134 at least partially resides within distal end 118 or supply lumen114. Protruding from distal end 136 of stem 132 can be fins 138 whichcontact the inner surface of supply lumen 114. In one aspect, fins 138allow stem 132 to be positioned within a central portion of lumen 114.For example, stem 132 can extend along the central axis of lumen 114. Inuse, cryofluid can flow around the full circumference of stem 132.

In one embodiment, fins 138 can be affixed to the inner surface of lumen114 using adhesive. In other embodiments, the fins and the supply lumen,along with stem 132 and dispersion member 130, can be manufactured asone piece. For clarity, FIG. 2B, depicting cross-section A-A, provides afront view of stem 132, fins 138, and supply lumen 114. However, this isbut one method of securing dispersion member 130 within cyrochamber 126.Various other methods of anchoring dispersion member 130 within thecyrochamber can be incorporated in alternative embodiments.

In practice, a pressurized refrigerant or cyrofluid can be released fromrefrigerant supply unit 104, enter proximal end 116 of supply lumen 114,flow down to distal end 118 of the lumen, past fins 138 and intocyrochamber 126. Upon entering the cryochamber, the fluid can deflectoff of dispersion member 130 configured to divert the fluid toward theinner wall of the chamber. Upon contact with the inner surface ofchamber 126, the fluid can begin to “boil,” or change into a gaseousstate, as it absorbs heat from tissue in contact with the outer surfaceof expandable member 200. The deflection of the cyrofluid by dispersionmember 130 can concentrate the refrigerant stream along acircumferential band around the inner diameter of cyrochamber 126.

FIG. 2C depicts this deflection from a front view. As the refrigerantexits distal end 118 of supply lumen 114 and strikes dispersion member130, the fluid can deflect off the dispersion member in a radialdirection and be directed towards the inner wall of cyrochamber 126. Theuniform distribution of the refrigerant in this fashion can facilitate aconsistent concentration of refrigerant at a circumferential band withinthe cyrochamber and result in a uniform ablation band at the targetedtissue.

In another aspect, the spent, or gaseous, refrigerant can then leavecyrochamber 126 through exit 127. In the embodiment depicted in FIG. 2A,exit 127 is located at the distal end of the cyrochamber. The cryofluidcan travel between the outer surface of cyrochamber 126 and the innersurface of exhaust chamber 128, towards the chambers proximal ends. Thespent cryofluid can then flow into distal end 124 of exhaust lumen 120and exit the system at proximal end 122 of the lumen. It should benoted, however, the exhaust of spent refrigerant can be accomplished invarious ways. Additional methods of exhausting the gas are describedbelow, though other methods can also be incorporated in differentembodiments and the methods described herein should not be consideredexhaustive.

Referring now to FIG. 3A, another method of anchoring dispersion member130 within cyrochamber 126 is depicted. In one aspect, cyrochamber 126can be subdivided by wall 140. In one embodiment, wall 140 can becomprised of the same material as cyrochamber 126. In other embodiments,wall 140 can be comprised of a more rigid material. For example, wall140 can be comprised of the same material as dispersion member 130 orthe two bodies, the dispersion member and the wall, can be integratedsuch that wall 140, in and of itself, functions as the dispersion memberand serves to divert refrigerant flow towards the inner wall ofcyrochamber 126.

In one embodiment, wall 140 can be a collapsible or foldable structurecapable of taking on a predetermined shape when an adjacent chamber ispressurized. For example, chamber 129, adjacent cyrochamber 126, can bepressurized to provide support to wall 140 and/or dispersion member 130.Alternatively, wall 140 can be porous such that cyrochamber 126 andchamber 129 can be pressurized concurrently in order to support wall 140and/or dispersion member 130. In another aspect, the axial location ofdispersion member 130 can be altered by changing the shape or positionof wall 140 within the cyrochamber. For example, FIG. 3A depicts wall140 at approximately the middle of cryochamber 126. This can result inthe refrigerant flow being diverted at that same axial position andforming an even refrigerant distribution band around the inner diameterof the cryochamber just proximate to wall 140. Alternatively, wall 140can be located at the distal or proximate ends of the cryochamber,resulting in a corresponding repositioning of the refrigerantdistribution band within the chamber.

FIG. 3B depicts an alternative shape for wall 140. In this embodiment,the wall spans less than the expandable chamber's entire diameter. As aresult, wall 140 can be comprised of a non-collapsible rigid materialwhile remaining small enough to traverse a patient's vasculature.Alternatively, wall 140 can be collapsible or foldable, such that istakes on a predetermined shape when cyrochamber 126 is pressurized.Regardless, chamber 129 can be expanded or constructed to adjust theposition of wall 140.

FIGS. 3A and 3B also depict an alternative flow path for spentrefrigerant from that depicted in FIG. 2A. In the embodiment depicted inFIGS. 3A and 3B, cyrochamber 126 can be coupled to exhaust lumen 120 atits distal end 124. This coupling can be achieved according to methodssimilar to those described above for coupling the cyrochamber to thesupply lumen. Supply lumen 114 can then be positioned concentricallywithin exhaust lumen such that both distal end 118 of the supply lumenand distal end 124 of the exhaust lumen are in fluid communication withthe cyrochamber.

Thus, in operation, refrigerant can be supplied to the cryochamberthrough the supply lumen and dispersion member 130 can deflect therefrigerant towards the inner wall of the chamber. The fluid deflectioncan provide a circumferential band of fluid around the inner diameter ofthe cryochamber resulting in a uniform ablation band at the targetedtissue. Upon absorption of heat, the refrigerant can become a gas andcan flow into distal end 124 of exhaust lumen 120 and out of the system.As mentioned above, however, there are other methods of allowing spentrefrigerant to exit the cyrochamber.

Referring now to FIG. 4A, another embodiment of the cyroablationcatheter is depicted. In one aspect, the cyroablation catheter depictedcan comprise a dispersion member 130 with a flow path therethrough. Inone aspect, the movement of fluid through the dispersion member cancause at least a portion of the dispersion member to rotate anddistribute cryofluid. FIG. 4A illustrates a rotary dispersion member 130including a proximal opening 142 and two distal openings 144 and 146.Openings 144 and 146 can be positioned proximate to the outermost endsof radially spaced arms 148 and 150, respectively. The flow path throughdistal arms 148 and 150, as well as distal openings 144 and 146, can bepositioned so as to redirect the refrigerant entering the dispersionmember at proximal opening 142 at various angles with respect to theflow exiting the supply lumen. In the embodiment depicted, this can beaccomplished using substantially U-shaped distal arms extending fromdispersion member 130. In other embodiments, however, distal arms 148and 150 and openings 142 and 144 can be configured so as to redirectrefrigerant flow at some other angle with respect to the fluid enteringthe dispersion member, depending on the distribution of refrigerantdesired.

Dispersion member 130 can be rotatably coupled to distal end 118 ofsupply lumen 114. This coupling can be accomplished in various ways,including, but not limited to, a slot and groove connection.Additionally, distal openings 144 and 146 can be configured so as toredirect flow in opposing directions. In this manner, when refrigerantexits supply lumen 114 and enters dispersion member 130 through proximalopening 142, the cyrofluid can be redirected through distal openings 144and 146. As a result of the rotatable coupling and the shape of distalarms 148 and 150, the forces resulting from the refrigerant exiting thedistal openings of the dispersion member can propel the dispersionmember and cause it to spin, distributing the exiting fluid in a uniformcircumferential band along the inner wall of cyrochamber 126. Forclarity, the rotation of dispersion member 130 and the distribution ofthe refrigerant is depicted in FIG. 4B.

Alternative embodiments can incorporate fewer or additional radiallyspaced distal openings in dispersion member 130, depending on thedesired distribution of cyrofluid within cyrochamber 126. For example,dispersion member 130 can comprise only one distal opening or it cancomprise three or more distal openings. Additionally, while thedispersion member depicted in FIG. 4A has circular distal openings,other embodiments can incorporate differently shaped openings. Forexample, distal openings 144 and 146 can have a slot-like shape in orderto achieve a desired pattern of distributed refrigerant or the openingscan be configured as narrowing nozzles if a higher velocity flow fromthe dispersion member is preferred. Additionally, distal arms 148 and150 can have a different shape in order to alter the reactive forces ofthe exiting refrigerant or otherwise alter the resulting refrigerantdistribution.

FIGS. 5A and 5B depict another embodiment of the invention. Asillustrated, dispersion member 130 does not move in response to fluidflow therethrough. Dispersion member 130 has a proximal opening 142coupled to distal end 118 of supply lumen 114 and tapering outward to alarger disc-like shape at its distal end. The distal end of dispersionmember 130 can be closed with the exception of a row of apertures 144located around its outer circumference. In other embodiments, dispersionmember 130 need not taper out to a disc-shape. For example, the distalend of the dispersion member can have a rectangular or cubic shape.

In another aspect, the proximal end of cyrochamber 126 can be coupled toexhaust lumen 120 in a manner previously described. Supply lumen 114 canbe concentric with exhaust lumen 120 and positioned within it.

In this embodiment, the cryofluid can exit the supply lumen, enter theproximal end of dispersion member 130 and be redirected out theplurality of apertures toward a circumferential band on the inner wallof cryochamber 126.

In another aspect, apertures 144 are cylindrical, but other embodimentscan incorporate openings of a different shape. For example, apertures144 can be in the shape of a slot. Alternatively, the apertures can benarrowing as they approach the outer surface of dispersion member 130,thereby increasing the velocity of the refrigerant flowing therefrom.Further, other designs can incorporate additional rows of apertures ormore or fewer apertures than depicted in FIGS. 5A and 5B. Otherembodiments can incorporate apertures that approach the outer surface ofdispersion member 130 at an angle, other than being substantially in theradial direction. Additionally, the axial location of the dispersionmember can be adjusted depending on the desired distribution ofrefrigerant.

Referring now to FIGS. 6A and 6B, another embodiment of the cryoablationcatheter is depicted. In one aspect, dispersion member 130 can becomprised of an expandable balloon similar to that of cyrochamber 126.These balloons can be comprised of a polyurethane or any other materialcommonly used in the art. Alternatively, dispersion member 130 can becomprised of a rigid material. Additionally, although dispersion member130 is depicted as spherical or substantially spherical in FIG. 6A,member 130 can also take on various other shapes. For example, inanother embodiment, the chamber of dispersion member 130 can becubically, or substantially cubically, shaped.

In one aspect, dispersion member 130 can exhibit a plurality ofapertures 144 in a circumferential band around its diameter. In theembodiment depicted, this band of apertures is located at the dispersionmember's approximate axial midpoint. However, in other embodiments, thisband can be located more proximate or more distal than depicted.

In practice, refrigerant exiting supply lumen 114 can enter dispersionmember 130 and, as a result of the pressure in the dispersion member,can be ejected through apertures 144 and directed toward acircumferential band on the inner wall of cyrochamber 126. This canresult in the even distribution of the refrigerant about a desiredsurface of the cyrochamber, corresponding to apertures 144 in thedispersion member. Further, although apertures 144 are depicted ascylindrical openings in the dispersion member, the apertures can bealtered in various ways in order to effect a change in the distributionof the refrigerant within the cryochamber. For example, apertures 144can be shaped as nozzles narrowing from the inner surface of dispersionmember 130 to the outer surface of the dispersion member if a highervelocity of refrigerant flow within cyrochamber 126 is desired.Alternatively, apertures 144 can be shaped as slots, rather thancylinders, if a wider distribution at the inner surface of thecyrochamber is desired. Additionally, the apertures can be shapeddifferently from one another as opposed to all being of one uniformshape. Various other configurations can also be envisioned.

In another aspect of this embodiment, while apertures 144 are depictedas encircling dispersion member 130, the apertures can be located onless than 360° of the dispersion member. For example, if, rather than acontinuous ablation band around the full circumference of the adjacenttissue, one desired to ablate only a portion of the circumference of thetargeted tissue, apertures 144 can be located across only a portion ofdispersion member 130. For example, apertures 144 could be locatedacross only 180°, 90°, or some other portion of the dispersion member.

Similarly, with respect to the embodiments depicted in FIGS. 2A-5B,dispersion member 130 can be configured to dispense cyrofluid along onlya portion of the full circumference of the cyrochamber.

Referring now to FIG. 7, another embodiment of the cyroablation catheteris depicted. In one aspect, a dispersion member 130 can reside withincyrochamber 126. In the embodiment depicted, dispersion member 130resembles a pyramidal or conical body, narrow at the proximal end ofcyrochamber 126 and widening out towards the mid-section of the chamber.However, in other embodiments, the shape of dispersion member 130,particularly the shape of the surface facing the distal end of supplylumen 114, can depend on the desired flow of the refrigerant withincyrochamber 126. For example, a less drastically tapering dispersionmember can be used if it is desired that the refrigerant be directedtowards the proximal end of the cyrochamber. Alternatively, a moredrastically tapering dispersion member can be used if it is desired thatthe refrigerant be directed more towards the distal end of cyrochamber126 or directed along the inner wall of the chamber rather than at thewall.

In the embodiment depicted, dispersion member 130 can be anchored inplace within cyrochamber 126 through the use of stem 132 having aproximal end 134 and a distal end 136. In one aspect, distal end 136 ofstem 132 can be coupled to dispersion member 130 while the proximal end134 at least partially resides within distal end 118 or supply lumen114. Protruding from distal end 136 of stem 132 can be fins 138 whichcontact the inner surface of supply lumen 114. In one embodiment, fins138 can be affixed to the inner surface of lumen 114. In otherembodiments, the fins and the supply lumen, along with stem 132 anddispersion member 130, can be manufactured as one piece. However, thisis but one method of securing dispersion member 130 within cyrochamber126. Various other methods of anchoring dispersion member 130 within thecyrochamber can be incorporated in alternative embodiments. For example,dispersion member could be affixed or built in to the distal wall of thecryochamber or could be affixed to a chamber wall, as shown in FIG. 3Aor 3B.

In practice, a pressurized refrigerant or cyrofluid can be released fromrefrigerant supply unit 104, enter proximal end 116 of supply lumen 114,flow down to distal end 118 of the lumen, past fins 138 and intocyrochamber 126. Upon entering the cryochamber, dispersion member 130can deflect the fluid toward the inner wall of the chamber. Thedeflection of the cyrofluid by dispersion member 130 can concentrate therefrigerant stream along the side walls of the cryochamber rather thanthe distal end of the cyrochamber.

In another aspect, the spent, or gaseous, refrigerant can then leavecyrochamber 126 through exit 127. In the embodiment depicted in FIG. 7,exit 127 is located at the distal end of the cyrochamber. In otherembodiments, however, the exit can be located elsewhere within thechamber. The refrigerant leaving cyrochamber 126 can then be containedby exhaust chamber 128, which houses the cyrochamber. The spentcryofluid can then be allowed to flow into distal end 124 of exhaustlumen 120 and exit the system at proximal end 122 of the lumen. Itshould be noted, however, the exhaust of spent refrigerant can beaccomplished in various ways. Additional methods of exhausting the gasare described above, though other methods can also be incorporated indifferent embodiments and the methods described herein should not beread to exclude other possible alternatives.

All the embodiments of the invention discussed above can be used toperform cyroablation of targeted tissue. A method of use can comprisethe provision of one of the cyrocatheters described and delivering arefrigerant to the distal end of the device, into the cyrochamber wherethe refrigerant is directed by a dispersion member toward and/or along adesired portion of the inner wall(s) of the chamber.

Additional features can also be incorporated into the cryoablationcatheter device to improve its functionality. For example, thecomponents of the device can be comprised of a medical grade materialsuitable for a surgical environment or a radiopaque material so as topermit visualization of the catheter during the procedure. In otherembodiments, force, pressure, strain, and/or temperature sensors can beincorporated into the device providing the surgeon with informationabout the refrigerant within the catheter and cyrochamber and thesurrounding targeted tissue. Additionally, conductive materials can beplaced or integrated into the inner surface of the cyrochamber and/orexhaust chamber to facilitate uniform cooling of the targeted tissue.Further, additional outer chambers can be used to house those discussedherein to moderate cooling and/or protect against rupture, breakage, andescape of the cryofluid.

The cyroablation catheter described herein can also be used to ablatetissue in other areas of the body aside from epicardial tissue. In fact,the device can be used in any ablative procedure that utilizes acryochamber at the distal end of a catheter body.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with the true scope and spiritof the invention being indicated by the following claims.

What is claimed is:
 1. A catheter device, comprising: an elongatecatheter body having a proximal end and a distal end; an expandableelement disposed at the distal end of the elongate catheter body, theexpandable element including an expandable external chamber and anexpandable internal chamber, the internal chamber adapted to receivecoolant from the distal end of the elongate catheter body, the internalchamber residing completely within the external chamber, the externalchamber configured to return the coolant to the proximal end of thecatheter body; wherein the external chamber and/or the internal chamberincludes a conductive material; and a dispersion member residing withinthe internal chamber and configured to direct a flow of coolant to apredetermined location, wherein the internal chamber has a proximal endand a distal end, the internal chamber including an inlet at theproximal end for receiving coolant and an outlet at the distal end forreleasing coolant into the external chamber.
 2. The device of claim 1,wherein the external chamber includes the conductive material.
 3. Thedevice of claim 1, wherein the internal chamber includes the conductivematerial.
 4. The device of claim 1, wherein the dispersion memberdirects the coolant in a radial direction.
 5. The device of claim 4,wherein the dispersion member directs the coolant around a fullcircumference of the expandable element.
 6. The device of claim 4,wherein the dispersion member directs the coolant around only a portionof a circumference of the expandable element.
 7. The device of claim 1,wherein the dispersion member directs the coolant towards a proximal endof the expandable element.
 8. The device of claim 1, wherein thedispersion member has a surface positioned so as to redirect the flow ofcoolant exiting the distal end of the elongate catheter body in a radialdirection, with respect to the elongate catheter body.
 9. The device ofclaim 1, wherein the dispersion member is anchored to the distal end ofthe elongate catheter body.
 10. The device of claim 1, wherein thedispersion member is connected to the distal end of the elongatecatheter body by a stem having a proximal end and a distal end, thedistal end of the stem coupled to the dispersion member and the proximalend of the stem coupled to the elongate catheter body.
 11. The device ofclaim 10, wherein the proximal end of the stem is coupled to theelongate catheter body by a plurality of fins protruding from theproximal end of the stem.
 12. A catheter device, comprising: an elongatecatheter body having a proximal end and a distal end; and an expandableelement disposed at the distal end of the elongate catheter body, theexpandable element including an expandable external chamber and anexpandable internal chamber, the internal chamber adapted to receivecoolant from the distal end of the elongate catheter body, the externalchamber configured to return the coolant to the proximal end of thecatheter body; wherein the external chamber and/or the internal chamberincludes a conductive material; and a dispersion member residing withinthe internal chamber and configured to direct a flow of coolant to apredetermined location, wherein the dispersion member is connected tothe distal end of the elongate catheter body by a stem having a proximalend and a distal end, the distal end of the stem coupled to thedispersion member and the proximal end of the stem coupled to theelongate catheter body by a plurality of fins protruding from theproximal end of the stem.
 13. The device of claim 12, wherein thedispersion member is configured such that when the coolant reaches thedispersion member, the dispersion member changes the direction of flowof the coolant away from a distal end of the expandable element andtowards a sidewall of the expandable element.
 14. The device of claim13, wherein the dispersion member is configured to concentrate the flowof the coolant along the sidewall of the expandable element.